You’ve got more than enough to do at calving time, but a little thought and a few notes now could be a great investment in your herd’s future. Do that and a Nebraska researcher figures you will have most of the information you need in your calving notes to choose the heifers you want to breed.
Rick Funston, of the Gudmundsen Sandhills Laboratory of the University of Nebraska, Lincoln, says the best way to find heifers that grow into cows that deliver a decent calf and stay in the herd year after year is to choose from calves born early in the calving season.
Don’t include heifers born to mothers with problems, but expose the rest to a 30- to 45-day breeding period to pick out the most fertile heifers as your replacements. If that’s more than you need, sell some as bred heifers.
Funston bases his advice on work at the U.S. Meat Animal Research Center (MARC) showing heifers calving early in their first calving season have increased longevity and wean more pounds of calf, compared to those delivering their first calf later in the season.
In his own research, Funston tracked over 1,100 heifers born from 1997 to 2009 from birth to second pregnancy and found a big advantage to those born in the first 21 days.
Those heifers as yearlings were more likely to be cycling at the start of the breeding season. They had a 90 per cent pregnancy rate and 81per cent calved in the first 21 days of their first calving season — the ones MARC says are most likely to become the ideal cow, delivering a decent calf year after year.
The number pregnant after weaning their first calf wasn’t significantly different from cows born in the third 21-days cycle, 93 per cent compared to 84 per cent, but it was higher. Choosing those older heifers is selecting for fertility, he says.
Not only were those heifers more fertile, they had lower birth weights, but being a few weeks older than calves born in the following 42 days, they had higher weaning weights. They maintained their weight advantage over younger animals into their first pregnancy even though later-born animals had slightly higher rates of gain.
Funston advises eliminating daughters of cows that need help calving, those with big teats that you have to help nurse and those with attitude problems. All these things really show up around calving time, and should be in your notes. Sometimes by weaning time a calf looks so good her mother’s flaws don’t seem so bad. But, that calf may well look a lot like her mother a couple of years from now. Calving is the time to think about whether that’s what you want.
The Edmonton-based, Delta Genomics, Igenity’s Canadian testing partner, is working to identify superior replacement heifers from DNA. They use fertility, longevity and feed efficiency markers as guides to maternal functions. It’s still early in their verification process, but they can give a score of 1 to 10 for each of those traits that allows you to rank animals in your herd.
“We don’t have the confidence and accuracy we’d like in our replacement female tests yet,” says Delta CEO, Colin Coros. “We need 2,000 or 3,000 animals to show our tests work, but ideally we’d like to validate them on 10,000 animals. We work by ranking a population, so the more animals the better. We’ve worked a lot with Angus cattle and our testing for them is quite accurate. Now we’re working on other cattle populations.
“Longevity, which is so important for replacements in cow-calf herds is very complex — so many traits are involved.”
DNA testing works by correlating records of an animal’s performance with the chemical reactions when a sample of its DNA is added to a number of specific DNA pieces or “snips,” each containing a known marker, Coros explains. At present, testing replacement heifer traits requires a panel of 50,000 snips. As more and more cattle are tested Coros expects they will be able to identify the most important markers so they can use fewer DNA snips but achieve greater accuracy and bring down the cost of testing from its present $25 per sample. Accuracy is better within breeds than in crossbreds and testing in very different environments can be more challenging, he says.
Eventually, Coros expects DNA results will be used like EPD values today to rank animals within a population.
“There is value to testing now,” he says. “The tests definitely allow you to rank animals for each trait. That should have some value in choosing among animals. But, the real value of this technology is that you can make decisions earlier in an animal’s life. And, other tests for negative traits in a population can eliminate some animals you don’t want to keep.”